Fundamentals of Error Correction MCQ || Error Correction Questions and Answers

1. GPRS stands for

  1. General Packet Radio Service
  2. Global Positioning Radio Service
  3. Geological Packet Radio Service
  4. Geological Positioning Radio Service

Answer.1. General Packet Radio Service


General Packet Radio Service

  • GPRS, or General Packet Radio Service, is a best-effort packet-switching communications protocol for cellular networks.
  • GPRS was one of the first widely used data transfer protocols on cellular networks.
  • GPRS is a third-generation step toward internet access.
  • GPRS is also known as GSM-IP is a Global-System Mobile Communications Internet Protocol as it keeps the users of this system online, allows them to make voice calls, and access the internet on the go.


2. Assertion A): If the frequencies are in the microwave range, H, Y, and Z parameters can not be measured.

Reason R): Short and open circuits are difficult to achieve over a broadband of frequencies and active devices such as power transistors and tunnel diodes, frequently will not have stability for a short or open circuit.

  1. Both A) and R) are true and R) is the correct explanation of A)
  2. Both A) and R) are true, but R) is not the correct explanation of A)
  3. A) is true, but R) is false
  4. A) is false, but R) is true

Answer.2. Both A) and R) are true, but R) is not the correct explanation of A)



If the signal frequency is in the microwave range, the widespread H, Y, and Z parameters (used in basic network theory) cannot be measured for the following reasons:

  • Equipment is not readily available to measure total voltage and total current at the ports of the networks.
  • Active devices may be unstable or self-destruct with short and open circuits

S-parameters measure traveling waves rather than total voltages and currents. The following are some advantages of using S-parameters:

  • The basic measurements to determine the S-parameters are familiar and well-established microwave measurements: reflection coefficient, attenuation (gain), phase
  • S-parameters are analytically convenient; they allow for calculations of system performance by cascading the individual components.
  • Flow-graph analysis can be used, which simplifies the analysis of a microwave system.

Statement I is true


Active devices such as power transistors &tunnel diodes frequently won’t have stability for a short or open circuit. Short circuits and open circuits are difficult to achieve over a wide range of frequencies.

Statement II is true


Microwave circuits are analyses using scattering (or) S parameters which linearly relate the reflected wave’s amplitude with those of incident waves.


3. Which system allows the entire bandwidth to be available to each user at the same time?

  1. CSMA
  2. GSM
  3. CDMA
  4. FDMA

Answer.3. CDMA


CDMA stands for Code Division Multiple Access.

  • It is a channel access method used by various radio communication technologies.
  • The principle of the spread spectrum is used to work with CDMA.
  • CDMA is not frequency specific to each user, instead, every channel uses the full available spectrum.
  • Each user in a CDMA system uses a different code to modulate their signal.

CSMA stands for Carrier Sense Multiple Access. 

  • It is a Media Access Control (MAC) protocol that is used to control the flow of data in transmission media so that packets do not get lost and data integrity is maintained. There are two modifications to CSMA:

1) CSMA CD (Collision Detection)

2) CSMA CA (Collision Avoidance)

FDMA stands for Frequency Division Multiple Access.

  • FDMA is a channel access method used in some multiple-access protocols.
  • FDMA allows multiple users to send data through a single communication channel, such as a coaxial cable or microwave beam, by dividing the bandwidth of the channel into separate non-overlapping frequency sub-channels and allocating each sub-channel to a separate user.
  • Users can send data through a sub-channel by modulating it on a carrier wave at the sub-channels frequency.
  • FDMA is not vulnerable to timing errors.


4. In layering, n layers provide service to

  1. n layer
  2. n-1 layer
  3. n+1 layer
  4. None of the mentioned

Answer.3. n+1 layer


In networking, layering means breaking up the sending of messages into separate components and activities. Basically, an N-layer application is partitioning application logic into specific layers. The N-layer architecture pattern is a mature architecture and simply refers to applications separate various logical layers into separate physical tiers.

In layering, n layer provides service to n+1 layer and uses the service provided by n-1 layer.


5. The final code after encoding data bits 1101 into 7-bit even parity Hamming Code is

  1. 1110101
  2. 1011101
  3. 1010101
  4. 0110101

Answer.3. 1010101


Hamming (7, 4) code: It is a linear error-correcting code that encodes four bits of data into seven bits, by adding three parity bits.

Example: It is used in the Bell-Telephone laboratory, an error-prone punch caret reader to detect the error and correct them.

Hamming code:

Bits # 1 2 3 4 5 6 7
Transmitted bits P1 P2 d1 P3 d2 d3 d4

P1 = d1 ⊕ d2 ⊕ d4

P2 = d1 ⊕ d4 ⊕ d3

P3 = d2 ⊕ d4 ⊕ d3


Given data 1101 i.e.

d1 = 1, d2 = 1, d3 = 0, d4 = 1

We can write:

P1 = d1 ⊕ d2 ⊕ d4 = 1 ⊕ 1 ⊕ 1 = 1

P2 = d1 ⊕ d4 ⊕ d3 = 1 ⊕ 1 ⊕ 0 = 0

P3 = d2 ⊕ d4 ⊕ d3 = 1 ⊕ 1 ⊕ 0 = 0

Then transmitted final code is

P1 P2 d1 P3 d2 d3 d4
1 0 1 0 1 0 1

i.e. 1010101


6. Which of the following can be used as an intermediate device in-between transmitter entity and receiver entity?

  1. IP router
  2. Microwave router
  3. Telephone switch
  4. All of the mentioned

Answer.4. All of the mentioned


Routers and switches are both computer networking devices that allow one or more computers to be connected to other computers, networked devices, or to other networks. IP router, microwave router, and telephone switch can be used as an intermediate device between the communication of two entities.


7. Which of the following codes uses a number of parity bits located at certain positions in the codeword and uses the relations between redundancy bits and the data bits?

  1. Unicode
  2. Morse code
  3. Hamming code
  4. Baudot code

Answer.3. Hamming code


Hamming codes are linear block codes. The family of (n, k) hamming codes for q ≥ 3 is defined by the following expressions:

1. Number of Block diagrams (n) = 2q – 1

2. Number of message bits (k) = 2q – q – 1

3. Number of Parity bits (q) = (n – k)

Hamming code is a set of error-correction codes that can be used to detect and correct ‘1’ bit errors that can occur when the bitstream is sent through the channel. It can be employed in both burst and signal error correction.


8. Which one of the following modes is called a two-way simultaneous, communication between two stations?

  1. Full duplex (FDX)
  2. Simplex (SX)
  3. Half-duplex (HDX)
  4. Full/Full-duplex (F/FDX)

Answer.1. Full duplex (FDX)


The data flow between the two devices can be in simplex, half-duplex, and full-duplex modes.

Full Duplex:

  • In Full-duplex mode, both stations can transmit and receive at the same time.
  • The channel capacity is shared by both communicating devices at all times. Example: Mobile phones


  • In Simplex, communication is unidirectional. Only one of the devices sends the data and the other one only receives the data.
  • The channel capacity is used by only one device all a time. Example: A CPU sends data while a monitor only receives data.

Half Duplex:

  • In half-duplex, both the stations can transmit as well as receive but not at the same time. When one device is sending others can only receive and vice-versa
  • The channel capacity is shared by both the devices but at a time only once the device uses the full capacity. Example: A walkie-talkie


9. Which has a comparatively high-frequency component?

  1. Sine wave
  2. Cosine wave
  3. Square wave
  4. None of the mentioned

Answer.3. Square wave


A square wave is a non-sinusoidal periodic waveform in which the amplitude alternates at a steady frequency between the fixed minimum and maximum values.

The square wave also called a pulse train, or pulse wave is a periodic waveform consisting of instantaneous transitions between two levels. The square wave has a comparatively high-frequency component in them.


10. The code rate of an (n,k) code is defined as:

  1. n/k
  2. k/n
  3. n-k/k
  4. n-k/n

Answer.2. k/n


  • In an (n,k) block code, the Information stream is partitioned into blocks of ‘k’ elements with each block mapped to a layer block of ‘n’ elements called code word.
  • The elements of a code block word are selected from an alphabet of ‘q’ symbols.
  • For a Binary code q = 2 and the alphabets are (0, 1)
  • For Non-binary code, q will be greater than 2

∴ The code rate Rc = K/n

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